Plot Occurrence Frequency

Tabulate observed taxon occurrence across assessable plots from a binary inventory; unassessable plots are excluded, not assumed absent, and occurrence is not stem density.

Description

Plot occurrence measures presence frequency, not stem density.

Plot occurrence measures presence frequency, not stem density. Unassessable plots must be excluded from the denominator instead of treated as absence.^[1]

Tabulate observed taxon occurrence across assessable plots from a binary inventory; unassessable plots are excluded, not assumed absent, and occurrence is not stem density.

When to use Plot Occurrence Frequency

Use this tool to tabulate observed taxon occurrence across assessable plots from a binary inventory; unassessable plots are excluded, not assumed absent, and occurrence is not stem density.

Gather the tree inventory, plot measurements or model parameters. Check diameter, area, time and moisture conventions; keep paired observations aligned.

How to use Plot Occurrence Frequency and understand its results

Gather the tree inventory, plot measurements or model parameters. Check diameter, area, time and moisture conventions; keep paired observations aligned.
Enter speciesPresenceByPlot, plotAssessableFlags using the field table and calculation rules, then run the tool.
Read assessablePlotCount, speciesOccurrencePercentages. The explanation below defines the units, signs, ordering and any flags or placeholder values.
If the tool reports an input issue, correct the values and run it again. Apply the stated assumptions when interpreting a successfully returned result.

Input field	Meaning	Value type; see rules below	Requirement
speciesPresenceByPlot	Species presence by plot	list of list of number	Required
plotAssessableFlags	Plot assessable flags	list of number	Required

Enter a rectangular plot-by-species binary matrix and aligned binary assessability flags. Require at least one assessable plot; return that count and taxon occurrence percentages in column order.

Paired lists must be nonempty and have equal lengths.

occurrence %=100 × assessable plots with taxon present/assessable plot count

Units, indexing, boundary conditions and exceptional cases are defined in the calculation rules above.

Output field	Meaning	Value type
assessablePlotCount	Assessable plot count	number
speciesOccurrencePercentages	Species occurrence percentages	list of number

json

{
  "input": {
    "speciesPresenceByPlot": [
      [
        1,
        0
      ],
      [
        0,
        1
      ],
      [
        1,
        1
      ]
    ],
    "plotAssessableFlags": [
      1,
      0,
      1
    ]
  },
  "output": {
    "assessablePlotCount": 2,
    "speciesOccurrencePercentages": [
      100,
      50
    ]
  }
}

Limitations and assumptions

No detection correction, abundance or population density is inferred.

Numeric inputs and returned numeric values must be finite; an unrepresentable returned value produces an error. Matrices are limited to 128 rows and 128 entries per row; other numeric lists are limited to 100,000 entries. Missing required fields, extra fields, wrong value types and violations of the calculation rules are input errors.

Alternative or Complementary methods

Use Species Importance Value: Calculate the three-component 0–300 importance-value convention from measured stems, basal area and plot occurrences; not percentage dominance alone or ecological importance certification. For a complementary task, use Understory Cover Percentage: Aggregate area-weighted understory point-layer cover, preserving overlapping layer totals separately from the union; unlike an existing single canopy-area percentage, multiple cover layers are not double counted in union.

References

Plot Occurrence Frequency — tool.io

Similar or alternative tools

Species Importance Value
Calculate the three-component 0–300 importance-value convention from measured stems, basal area and plot occurrences; not percentage dominance alone or ecological importance certification.
Understory Cover Percentage
Aggregate area-weighted understory point-layer cover, preserving overlapping layer totals separately from the union; unlike an existing single canopy-area percentage, multiple cover layers are not double counted in union.